The invention relates to an active or passive ossicular prosthesis, which is designed to replace or bridge at least one element of the human ossicular chain and comprises a sound-conducting, elongated prosthesis body, which on one end has a first coupling element designed as a top plate for placement of the prosthesis against the tympanic membrane, as a clip for the mechanical connection to a component of the ossicular chain, such as the limb of incus or the manubrium of malleus, or as a connecting piece for the sound-conducting connection to an actuator end piece of an active hearing implant. On the other end, the prosthesis body comprises a second coupling element having an access opening in a receiving space designed as a bell or clip for a mechanical connection of the prosthesis to the stapes, such as the head of stapes (“caput”).
Passive ossicular prostheses are described in the field of active hearing implants, such as in U.S. Pat. No. 6,537,199 B1 or, for example, in DE 10 2010 046 457 B3.
In conventional passive ossicular prostheses, such arrangements having differently designed first and second fastening elements are used, such as described in U.S. Pat. No. 5,514,177, in WO 98/16175 A1, in EP 1 181 907 B1, in DE 10 2008 015 117 B3 or in DE 10 2009 016 468 B3.
The human middle ear comprising the ossicles thereof has the function of transmitting the sound waves impacting the tympanic membrane via the external auditory meatus to the inner ear, which is filled with fluid. The three ossicles are the hammer (lat. malleus), which is fastened to the tympanic membrane, the stirrup (lat. stapes), which is connected via the footplate (lat. basis stapedis) thereof to the inner ear, and the anvil (lat. incus), which is located between the hammer and the stapes and is hingedly connected thereto.
Chronic middle ear inflammation is a disease of the human petrosal bone (=bone in which the entire ear is seated), in which degenerative processes can occur on the ossicular chain in a pathologically aggressive manner. As a result, the sound signal is not transmitted to the inner ear, or is transmitted incompletely, which results in conductive deafness.
Hearing implants are used to conduct the sound that impacts the auricle, or a corresponding sound signal, to the inner ear in cases in which the ossicles of the human middle ear are missing or damaged, entirely or in part. A distinction is made between passive ossicular prostheses and active hearing implants. Passive ossicular prostheses physically replace parts of the ossicular chain, wherein sound is conducted “passively”, i.e., without the aid of powered auxiliary means. Active hearing implants receive powered signals corresponding to the sound signals from an amplifier by use of an actuator implanted in the middle ear. The amplifier is usually electronic and is associated with an externally or an internally mounted hearing aid. Such active hearing implants convert these signals at this point via mechanical motion back to acoustic oscillations and transmit these from a vibrating actuator end piece to the inner ear via a suitable connecting element.
Passive ossicular prostheses are used to improve sound transmission in patients having different pathologies. These passive ossicular prostheses are used to conduct sound from the tympanic membrane to the inner ear in cases in which the ossicles of the human middle ear are missing or damaged, either entirely or partially. The ossicular prosthesis has two ends. Depending on the specific circumstances, one end of the ossicular prosthesis is fastened to the tympanic membrane, e.g., using a top plate, and the other end of the ossicular prosthesis is fastened to the stapes of the human ossicular chain, or it is inserted directly into the inner ear. In the known ossicular prostheses, sound conduction between the tympanic membrane and the inner ear is often limited because these known ossicular prostheses cannot fully replace the natural anatomical formations of the ossicular chain and the mechanisms of the middle ear, which have fine structures.
Three types of ossicular prostheses that are used particularly frequently are stapes prostheses, partial prostheses and total prostheses. Stapes prostheses are fixed to the incus and extend via a plunger into the inner ear. Partial prostheses typically bear via a top plate against the tympanic membrane and establish a connection to the head of the stapes. Total prostheses connect the tympanic membrane to the base of the stapes. The present invention relates exclusively to partial prostheses.
As shown clearly in the three enlarged photographs of more or less pathological human ear stapes bones in FIGS. 9a, 9b and 9c, the anatomical differences are drastic in terms of shape and absolute size. That is, the respective detailed views of FIGS. 9a-c specifically highlight the region of the head of the stapes, which is precisely where the above-described partial prostheses are supposed to be coupled via the second attaching element thereof. A truly optimal coupling at this position would therefore require that the shaping of the particular coupling element on the implant that is used be adapted in an entirely individualized manner for each patient, which cannot be done, of course, at a reasonable expense.
For that matter, a notable detail problem is that, in the case of the common forms of coupling elements that are known and have been used for many years (for example in embodiments such as a stapes bell, or when clips are used), a hollow space practically always forms as an extension of the shank-shaped prosthesis body between the inner side of the attaching element and the upper region of the head of the stapes because the stapes upper region usually has a somewhat flattened shape, while the coupling elements typically used at this point are concavely arched.